Detachable bit



April 3, 1934. B E KER 1,953,095

EEEEEEEEEEEE T 9 Filed Jul I 11/}; A Z 5' 4 3 g I 7 V I g ,V 7 v Patented Apr. 3, 1934 DETAClIABLE arr John B. Baker, Canton, Ohio, asslgnor to The Timken Roller Bearing Ohio, a corporation of Ohio Company, Canton,

Application July is, 1931, Serial No. 551,685

' 3 Claims. (01. 255-64) My invention relates to detachable bit constructions and has for its principal objects a screw thread arrangement therefor which will not bind and which is capable of withstanding the heavy 6 shocks resulting from drilling operations. Great diificulty has been experienced in finding thread constructions suitable for such use, most threads soon becoming jammed so as to prevent disassembly of the parts, or breaking off under the heavy shocks and stresses. The thread constructions of the present invention satisfactorily meet the requirements. The invention consists in providing the rear faces of at least one thread member with. a substantially straight profile. It further consists in the detachable bit construction and in the parts and combinations and arrangevnients of parts hereinafter described and claimed.

In the accompanying drawing,

, Fig. 1 is an elevation, partly in longitudinal section, of a detachable bit construction whose threaded connections embody my invention.

Fig. 2 is a view similar to Fig. 1 of the parts in detached position, the metal coupling member only being shown in longitudinal section; and

Figs. 3, 4, 5 and 6 are detail sectional views of several modifications of screw threads embodying my invention. 1

The drawing illustrates my invention as embodied in a detachable bit construction including a drill'rod 1 having a tapering threaded end portion 2., a bit member 3 having a tapering threaded shank 4 and a hollow coupling member 5 having tapering threaded-bores to cooperate with said shank 4 and with said drill rod 1. According to my invention, the front faces 6 of all of the threads are rather short and are disposed substantially flatwise to the end thrust to which they are subjected. The rear faces of all of the threads (indicated generally by the letter A) are comparatively long, making a comparatively small angle with the axis of the drill rod; and the rear face of at least one thread is convexly curved endwise.

' thread. In the construction shown in Fig. 3, the rear face 8 of the thread of the inner member (drill rod 1 or bit shank 4) is convexly curved endwise so to have a convex section or profile. The rear face 9 of the thread of the coupling member 5 is substantially straight in profll In the construction shown in Fig. 4, the rear face 19 of the thread of the coupling member 5 is convexly curved, the rear face 18 of the thread ofthe inner member being substantially straight. In the construction shown in Fig. 5, the rear A space 7 is left at the crest of each faces 28 and 29 of both sets of threads are convexly curved but are provided with straight zones 25 at their middle portions.

In the construction shown in Fig. 6, the rear faces 38 and 39 of both inner and outer members are convexly curved.

The convex curvature of one thread cooperating with the construction of the other thread whereby there is limited contact between the two threads makes the threads cooperate together easily and prevents jamming of the threads. Heavy shock and wear may flatten said curves; but extraordinarily long service is required to cause sufiicient flattening of the curves to permit the threads to bind. Previous curved thread constructions have included mating, closely fitting continuous curves on both thread members; and the important advantages of the present construction depend upon the absence of such mating thread surfaces.'

What I claim is:

1. A detachable bit construction comprising an internally threaded coupling member and externally threaded drill rod and bit shank, the front faces of all of said threads being comparatively short and disposed substantially flatwise with respect to end thrust and the rear faces of said threads being rather long, the rear face of one of each contacting pair of said threads being convexly curved endwise.

2. A detachable bit construction comprising an internally threaded coupling member and externally threaded drill rod and bit shank, the front faces of all of said threads being comparatively short and disposed substantially fiatwise with respect to end thrust and the rear faces of said thread being rather long, the rear faces of the threads of 'said coupling member being substantially straight in profile and the cooperating rear faces of the threads of said drill rod and of said bit shank being convexly curved in profile.

3. A detachable bit construction comprising an internally threaded member and an externally threaded member, the front faces of said threads being comparatively short and disposed substan tially flatwise with respect to end thrust and the rear faces of said threads being rather long, the rear face of one of each contacting pair of said threads being convexly curved endwise.

' JOHN B. BAKER. 

